The present invention relates to a method of wrapping a product in a sheet of heat-seal wrapping material.
The present invention is particularly advantageous for use on machines for cellophaning packets of cigarettes, to which the following description refers purely by way of example.
Known machines for cellophaning packets of cigarettes normally comprise a step-operated first wrapping wheel on which a sheet of heat-seal wrapping material is wound about a packet of cigarettes to form a tubular wrapping, which is stabilized by means of a longitudinal seal, and which comprises two tubular end portions, each projecting from a respective end wall of the packet. The longitudinal seal is made by a sealing device mounted at a fixed sealing station, and which, at each stop of the first wrapping wheel, is brought into contact with a longitudinal overlap portion of two opposite portions of the sheet of wrapping material.
At the output of the first wrapping wheel, the packet and respective tubular wrapping are normally fed through a folding station where the projecting tubular portions of the tubular wrapping are folded onto respective end walls to form two further overlap portions closing the ends of an outer overwrapping. The two overlap portions are then stabilized by two end seals as the packet is conveyed on a continuously operated second wrapping wheel.
Finally, the overwrapped packet is normally fed to an output station where it is normally heat treated to shrink the outer wrapping about the packet.
Known cellophaning machines of the type described above have several drawbacks, mainly due to the fact that, over and above a given operating speed, the stops of the first wrapping wheel are not long enough to enable correct execution of the longitudinal seal.
Moreover, a further drawback of known cellophaning machines of the type described above lies in the longitudinal seal being made separately from the end seals, which means the tubular wrapping, at the output of the first wrapping wheel, may undergo localized heat shrinking at the longitudinal overlap portion only, thus impairing correct formation of the outer wrapping by shortening and tightening the overlap portion with respect to the rest of the tubular wrapping.
It is an object of the present invention to provide a method of wrapping a product in a sheet of heat-seal wrapping material, designed to eliminate the aforementioned drawbacks.
According to the present invention, there is provided a method of wrapping a product in a sheet of heat-seal wrapping material, the method comprising the steps of wrapping the product in said sheet of wrapping material to form a tubular wrapping comprising a longitudinal first overlap portion, defined by superimposed portions of said sheet of wrapping material, and two projecting tubular end portions; folding each of said tubular end portions onto the product to form an outer wrapping having two further end overlap portions; and feeding said product along a sealing path, along which, said three overlap portions are stabilized by three sealing operations; and being characterized in that said product is fed along said sealing path by a respective same pocket, which is fed continuously along the sealing path.
The present invention also relates to a machine for wrapping a product in a sheet of heat-seal wrapping material.
According to the present invention, there is provided a machine for wrapping a product in a sheet of heat-seal wrapping material, the machine comprising first wrapping means for wrapping the product in said sheet of wrapping material and forming a tubular wrapping comprising a longitudinal first overlap portion, defined by superimposed portions of the sheet of wrapping material, and two projecting tubular end portions; second wrapping means for folding each said tubular end portion to form an outer wrapping having two further end overlap portions; sealing means located along a sealing path, and each for performing a respective sealing operation on a respective said overlap portion; and conveying means for feeding said product along said sealing path; and being characterized in that said conveying means comprise a single conveying pocket for said product; first actuating means being provided to feed said pocket continuously along said sealing path.